The Gilbreth family drinks a case of Royal Cola every
day, 365 days a year. Fortunately, a local distributor offers
quantity discounts for large orders as shown in the table
below, where the price for each category applies to every case
purchased. Considering the cost of gasoline, Mr. Gilbreth
estimates it costs him about $5 to go pick up an order of
Royal Cola. Mr. Gilbreth also is an investor in the stock
market, where he has been earning a 20 percent average annual
return. He considers the return lost by buying the
Royal Cola instead of stock to be the only holding cost
for the Royal Cola.
Discount Category
Quantity Purchased
Price (per Case)
1
1 to 49
$4.00
2
50 to 99
$3.90
3
100 or more
$3.80
a) Determine the optimal order quantity
according to the EOQ model with quantity discounts. What is
the resulting total cost per year?
b) With this order quantity, how many orders
need to be placed per year? What is the time interval between
orders?